This invention relates to composite structures and their preparation, and, more particularly, to a composite structure useful in hypersonic missiles that must withstand high aerothermal temperatures for a short period of time.
Some types of short-range missiles fly at several times the speed of sound and carry enough fuel to fly at most for a few minutes. The structural components of such missiles must withstand high mechanical loadings, surface abrasion and impact damage, and chemical attack over a wide skin temperature range of ambient temperature at launch to over 2000.degree. F. during flight. The structures must also protect the sensitive electronic and other devices located within the missile from the heat generated by skin friction as the missile flies.
The materials and structural configurations of the airframe are selected to function under the most extreme of these conditions, which are usually those encountered at the highest temperatures. Structural materials for use at high temperatures include metals such as steel and nickel alloys, ceramics, and some types of composites. Special types of structures such as honeycombs made from these materials are employed where appropriate. Additionally, ablative thermal protective systems can be used in some instances.
Each of these existing structural and protective approaches has drawbacks. The metallic alloys and ablative systems are heavy in relation to the structural strength and stiffness they provide. Ceramics tend to crack and fail prematurely. The available high-temperature organic-matrix composites provide marginal capability, while utilizing exotic organic compounds and processing which are potentially hazardous to human health. Most of these approaches are expensive to implement. Moreover, with the exception of ablative systems, the available structural techniques often provide more capability that is required for the short-range missile. The use of a nickel-alloy structural element, for example, typically provides high-temperature capability sufficient for hours of exposure, not just the few minutes of exposure required for the missile application.
There is a need for an improved approach to the materials and structures used in short-range, hypersonic missiles and other devices operating for relatively short periods of time in extreme-temperature and hostile environments. The present invention fulfills this need, and further provides related advantages.